1. Field of the Invention
The present invention relates to an input device for inputting information corresponding to an operation, a control method of the input device, and a program.
2. Description of the Related Art
A sensor for detecting a change in electrostatic capacitance can detect the approach of an object (for example, a fingertip or a pen) with a simple configuration. For this reason, such a sensor is widely used in user interface devices of various electronic apparatuses, such as a touch pad of a notebook computer or a touch panel of a smart phone. In addition, there is also a device in which a conductive operating member is disposed along the outer edge of such a sensor so that an operation on the operating member (for example, an operation of pinching the operating member with fingertips) is detected based on a change in electrostatic capacitance in the vicinity of the outer edge of the sensor.
Generally, in this type of sensor, the approach of an object is detected based on a difference value (detection value−base value) from a base value corresponding to a detection value of the electrostatic capacitance in a state in which the object is not close. Since the change in electrostatic capacitance according to the approach of an object is very small, the detection value of the sensor is likely to be influenced by the temperature characteristics of an electronic circuit or the like. If the detection value changes according to the temperature, the difference value from the base value is also changed. Accordingly, the approach of the object may be erroneously determined. Typically, therefore, a fixed value is not used as a base value, and processing for updating the base value at an appropriate timing is performed. For example, Japanese Unexamined Patent Application Publication No. 2010-257046 discloses a proximity detection device that updates a base value when it is determined that an object, such as a fingertip, is not close.
However, a temperature change in the environment of use may occur even in a state in which an object is close to the detection surface. Generally, in a known device that detects the approach of an object based on the difference between the base value and the detection value, the base value is not updated during a period in which the object is determined to be close. Therefore, when a large temperature change occurs during the period, the approach of the object may be erroneously determined.
In addition, in the environment of use, such as the inside of a vehicle, a large temperature change is likely to occur in a short period of time. Accordingly, it is necessary to further consider the erroneous determination described above. For example, in a case where the above operating member disposed along the outer edge of the sensor is intended to adjust the temperature of an air conditioner, a temperature change inside the vehicle is likely to occur in response to the operation of the operating member. Thus, in a known device, there is a disadvantage in that it is not possible to respond to temperature changes or the like in a case where an object is close.